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Volumes persistentes e solicitações de volumes persistentes

Entenda como provisionar e consumir armazenamento dinamicamente no Kubernetes usando PVs e PVCs.

Volumes persistentes e solicitações de volumes persistentes é uma aula grátis de Docker & Kubernetes for Developers no CoddyKit. Esta é a aula 1 de 4. Você pode ler a aula completa abaixo gratuitamente — depois pratica ao vivo no navegador com um editor de código integrado e um tutor de IA 24/7. Faz parte do caminho de aprendizado de Docker & Kubernetes for Developers, e seu progresso é sincronizado entre a web e o app CoddyKit. O curso de Docker & Kubernetes for Developers inclui 4 aulas no total.

Partes desta aula ainda não foram traduzidas e aparecem em inglês.

Ephemeral Pods, Persistent Data

In Kubernetes, Pods are designed to be temporary and replaceable. If a Pod crashes or is rescheduled, any data stored directly within it is lost.

This ephemeral nature is great for stateless applications, but what about applications that need to store data persistently, like databases or file servers?

Introducing Persistent Volumes

A Persistent Volume (PV) is a piece of storage in the cluster that has been provisioned by an administrator or dynamically by Kubernetes.

It's an abstraction of the underlying storage (like a cloud disk, NFS share, or local disk), making it available for use by Pods without them needing to know the storage's specifics.

PV Capacity & Access Modes

Each PV has specific characteristics:

  • Capacity: The size of the storage, e.g., 10Gi.
  • Access Modes: How the storage can be mounted by Pods.
  • Reclaim Policy: What happens to the volume after a Pod is done using it.

These properties help Kubernetes match storage requests to available volumes.

How Pods Access Storage

PV Access Modes define how the volume can be mounted:

  • ReadWriteOnce (RWO): The volume can be mounted as read-write by a single node.
  • ReadOnlyMany (ROX): The volume can be mounted as read-only by many nodes.
  • ReadWriteMany (RWX): The volume can be mounted as read-write by many nodes.

Not all storage types support all modes. For example, a local disk typically only supports RWO.

Handling Released PVs

A PV's Reclaim Policy dictates what happens to the underlying storage when the PV is released from its claim:

  • Retain: Manual reclamation. Data remains, administrator must manually delete.
  • Delete: The underlying storage is automatically deleted along with the PV. This is common for dynamically provisioned volumes.
  • Recycle: (Deprecated) Wipes the volume and makes it available again.

Retain is useful for critical data that needs manual review before deletion.

Requesting Persistent Storage

A Persistent Volume Claim (PVC) is a request for storage by a user or application.

Think of it like a request for a specific type and size of storage. Instead of directly interacting with PVs, Pods request storage through PVCs.

PVCs provide a layer of abstraction, allowing developers to request storage without knowing the underlying infrastructure details.

Matching Storage Requests

When a PVC is created, Kubernetes tries to find a suitable PV to bind it to. This process is called binding.

It looks for PVs that meet the PVC's requirements:

  • Capacity (size)
  • Access Modes
  • Storage Class (if specified)

Once bound, the PV is exclusively reserved for that PVC.

Defining a Basic PV

Here's how you might define a simple hostPath Persistent Volume. This type uses a directory on the node's filesystem, primarily for single-node testing.

Try running this example (kubectl apply -f pv.yaml):

apiVersion: v1
kind: PersistentVolume
metadata:
  name: my-pv
spec:
  capacity:
    storage: 1Gi
  volumeMode: Filesystem
  accessModes:
    - ReadWriteOnce
  persistentVolumeReclaimPolicy: Retain
  hostPath:
    path: "/mnt/data"

Requesting Storage with a PVC

Now, let's create a Persistent Volume Claim that requests 1Gi of storage with ReadWriteOnce access. It will bind to our my-pv if available.

Try running this example (kubectl apply -f pvc.yaml):

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: my-pvc
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 1Gi

Attaching PVC to a Pod

Finally, let's see how a Pod can use the storage provided by our PVC. We reference the PVC in the Pod's volumes section and then mount it into a container.

Try running this example (kubectl apply -f pod.yaml):

apiVersion: v1
kind: Pod
metadata:
  name: my-app-pod
spec:
  volumes:
    - name: my-storage
      persistentVolumeClaim:
        claimName: my-pvc
  containers:
    - name: my-container
      image: busybox
      command: ["sh", "-c", "echo 'Hello from CoddyKit!' > /data/message.txt && sleep 3600"]
      volumeMounts:
        - mountPath: "/data"
          name: my-storage

PV vs. PVC Roles

Understanding the distinct roles of Persistent Volumes (PVs) and Persistent Volume Claims (PVCs) is crucial for managing storage in Kubernetes.

Which statement accurately describes the primary role of a Persistent Volume (PV)?

Recap: Persistent Storage

Great job! You've learned how Kubernetes manages persistent storage:

  • Persistent Volumes (PVs) abstract physical storage resources.
  • Persistent Volume Claims (PVCs) are user requests for storage.
  • PVs have capacity, access modes (RWO, ROX, RWX), and reclaim policies (Retain, Delete).
  • PVCs bind to available PVs, and Pods then use PVCs to mount storage.

This system allows applications to reliably store data, even when Pods are recreated or moved.

Perguntas Frequentes

A aula “Volumes persistentes e solicitações de volumes persistentes” é grátis?

Sim — o texto completo de “Volumes persistentes e solicitações de volumes persistentes” é grátis para ler aqui na web. Para praticá-la interativamente (um editor de código integrado e um tutor de IA 24/7) e desbloquear o restante do curso de Docker & Kubernetes for Developers, atualize para CoddyKit PRO. O curso de Docker & Kubernetes for Developers inclui 4 aulas no total.

O que vou aprender em “Volumes persistentes e solicitações de volumes persistentes”?

Entenda como provisionar e consumir armazenamento dinamicamente no Kubernetes usando PVs e PVCs. Você pratica Docker & Kubernetes for Developers com código prático que executa diretamente no navegador, e um tutor de IA 24/7 responde suas dúvidas enquanto trabalha na aula.

Preciso ter experiência prévia para começar Docker & Kubernetes for Developers?

Nenhuma experiência prévia é necessária. Docker & Kubernetes for Developers no CoddyKit é estruturado para alunos iniciantes até avançados, então você pode começar aqui ou desde o início e aprender no seu ritmo. Esta é a aula 1 de 4.

Quanto tempo leva a aula “Volumes persistentes e solicitações de volumes persistentes”?

A maioria das aulas CoddyKit leva cerca de 5–10 minutos. Cada uma é compacta e interativa, então você faz progresso constante e retoma exatamente de onde parou entre web e app.

Posso escrever e executar código nesta aula de Docker & Kubernetes for Developers?

Sim. Cada aula de Docker & Kubernetes for Developers inclui um editor de código integrado, então você escreve e executa código real direto no navegador e recebe feedback de IA instantaneamente — nenhuma configuração local necessária.

Todas as aulas deste curso

  1. Volumes persistentes e solicitações de volumes persistentes
  2. Gerenciamento de aplicações com estado usando StatefulSets
  3. ConfigMaps e Secrets para configuração
  4. Classes de armazenamento e provisionamento dinâmico
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